In recent years the market of the semiconductor industry has grown considerably for supplying integrated chips to companies which manufacture portable electronic device. The integrated chips used to make these portable electronic device, such as cell phones, PDAs, laptop computers and the like, are mostly made in emerging technology nodes. This is because emerging technology nodes offer higher density chips with greater performance and lower power consumption. These qualities are important to portable electronic devices which are continually striving to offer greater functionality while relying on relatively small energy sources (e.g., batteries). The demand for these products has driven the industry to devote many resources to developing low power integrated chips, often resulting in specific processes.
One aspect of power consumption in integrated circuits is the power consumption of memory cells. There are two main types of memory, volatile memory and non-volatile memory. Volatile memory (e.g., SRAM, DRAM) is memory which requires power to retain its information. Non-volatile memory (e.g., EEPROM, flash) is memory which does not require power to retain its information. In recent years the use of non-volatile memory has become common place in portable electronics. Many portable electronic devices such as cell phones or digital cameras will rely upon a stick or card which uses flash memory as storage. Unfortunately, the performance and density of flash memory and other wide spread commercially available non-volatile memory sources lag behind that of volatile memory.
To amend this problem the semiconductor industry has put an increased emphasis on research into ferroelectric memory. Ferroelectric random-access memory (FRAM) is a non-volatile random access memory that offers advantages in terms of power consumption and write speed over existing non-volatile memory sources such as flash or EEPROM. FRAM memory utilizes a ferroelectric material as a dielectric for memory array capacitors. Due to the use of a ferroelectric material rather than traditional dielectrics, reliability of FRAM memory cells face new problems not present in traditional memory types. One such problem occurs when FRAM memory cells remain in the same data state for a prolonged period of time. They will develop a preference to stay in that particular data state. This preference for a particular state drives an increase in signal margin loss over time, resulting in device degradation and reliability concerns.